A horizontal line has a constant $y$-value, regardless of the $x$-value. The equation of a horizontal line passing through any point $(x_1, y_1)$ is simply $y = y_1$.

Since the line passes through the point $(8, -7)$, the $y$-value is $-7$. Therefore, the equation of the horizontal line is:

$y = -7$

Would you like further details or clarifications?

Here are 5 related questions to consider:

1. What is the equation of the vertical line passing through the point $(8, -7)$?
2. How do the equations of horizontal and vertical lines differ?
3. What is the slope of a horizontal line, and why?
4. How would the equation change if the line was not horizontal but had a slope?
5. How can you find the distance between two points on a horizontal line?

Tip: The slope of a horizontal line is always zero since the $y$-value remains constant across all $x$-values.